Communications: radio wave antennas – Antennas – With housing or protective covering
Patent
1999-03-23
2000-08-29
Wong, Don
Communications: radio wave antennas
Antennas
With housing or protective covering
342 1, 342 4, 428920, 523136, 523137, 156254, G21F 110, H01Q 136, B32B 3118
Patent
active
061115517
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a housing with radar-absorbent properties.
For equipment that generates radar radiation in the microwave range, housings must be created that at least in some regions also have radar-absorbent properties. Typical metal or plastic housings must have a foil or film glued to them that has these radar-absorbent properties.
For instance, it is known from European Patent Disclosure 0 685 340 Al that for a radar-absorbent window lining, a plurality of absorbent layers have to be glued to the window glass; one layer is provided with electric conductor segments in the form of wires, which are arranged parallel to one another as a function of the polarization of the incident radar beams, and which are adapted in terms of their size and installed position to the frequency of the radar beams to be absorbed.
Affixing additional absorber layers to housings for radar technology is very labor-intensive, and for many housing forms can be done with difficulty if at all.
SUMMARY OF THE INVENTION
In accordance with the present invention, the housing with radar-absorbent properties comprises electrically conductive particles with dimensions adapted to a frequency of radar beams to be absorbed; and a housing part composed of a material which has plastic as a basic component, selectively a mineral filling, and steel fibers as an additive in a mixture such that a specific conductivity .sigma. of said housing parts meets the following condition: said housing part, and
The housing with radar-absorbent properties according to the invention is advantageous because a housing can be produced in a single operation, for instance by injection molding in which the reinforcement and the additive are mixed with the basic component, and the radar-absorbent properties are always assured.
In a preferred embodiment, a housing is made, preferably injection-molded, from a plastic with a reinforcement comprising at least up to 50 weight-% of glass fibers, a filler or outfitting with up to 50 weight-% of mineral fillers or a mixture thereof, and an additive comprising approximately 5 to 20 weight-% of steel fibers. Thus in a simple manner a radar-absorbent housing can be made that with respect to its conductivity .sigma. meets the following physical condition: material, and
For example, at a frequency of over 10 GHz of the radar beams to be absorbed, a homogeneous conductivity of approximately 10 S/m is attainable, and the glass fibers in the plastic have a length of approximately 2 to 20 mm.
In another advantageous embodiment of the invention, the housing is also metallized on the outside, for instance chemically, galvanically, by vapor deposition or by sputtering.
BRIEF DESCRIPTION OF THE DRAWING
An exemplary embodiment of a housing according to the invention will be described in conjunction with the drawing. Shown are:
FIG. 1, a perspective view of a housing for a radar sensor in automotive engineering, and
FIG. 2, a basic illustration of a steel fiber filler in the housing material.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, a perspective view of a housing 1 for a radar sensor, not visible here, is shown. Such a radar sensor is a component of an ACC (Adaptive Cruise Control) vehicle security system, for instance, in which information on the distance from and relative speed with respect to other vehicles and on road conditions is continually processed. For example, in a manner known per se, FMCW (frequency modulated continuous wave) radar is mounted on the front of the outside of the vehicle and has an oscillator, a mixer, an amplifier, and an antenna system for generating the radar beams, as well as a receiver with evaluation electronics.
In the housing part shown in FIG. 1, in whose opening the antenna system is installed and which thus broadcasts toward the front, the plastic mixtures mentioned in the background section are provided for the sake of achieving adequate rearward absorption of the radar beams. FIG. 2, to show clearly the location of the steel fibers as an addit
REFERENCES:
patent: 4538151 (1985-08-01), Hatakeyama et al.
patent: 5223849 (1993-06-01), Kasevich et al.
patent: 5230763 (1993-07-01), Roth et al.
patent: 5552455 (1996-09-01), Schuler et al.
Clauss Georg
Langenhan Dirk
Lucas Bernhard
Moosbrugger Egon
Schmidt Ewald
Clinger James
Robert & Bosch GmbH
Striker Michael J.
Wong Don
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